1. Field of the Invention
The present invention relates to networks, and more particularly to prevent disruptions in networks.
2. Background of the Invention
In a common-access network, every attached network device detects all traffic on the network, and each device determines through network-specific hand shaking when to claim data from the network. Examples of common-access networks include Ethernet, Fibre Channel—Arbitrated Loop (FC-AL), and Token-Ring.
Because each device detects all traffic on a common-access network, certain behaviors from a single network device would disrupt all network devices. For example, a FC-AL device may initiate loop initialization and disrupt all traffic in FC-AL. Similarly; a beaconing condition would disrupt all traffic on a Token-Ring network.
Hence, isolation of disruptive events (or devices) is a challenge for modern networks. The following introduces Fibre Channel standards/terminology and also describes some of the challenges that a FC-AL topology faces in this context.
Fibre channel is a set of American National Standard Institute (ANSI) standards, which provide a serial transmission protocol for storage and network protocols such as HIPPI, SCSI, IP, ATM and others. Fibre channel provides an input/output interface to meet the requirements of both channel and network users.
Fibre channel supports three different topologies: point-to-point, arbitrated loop and fibre channel fabric. The point-to-point topology attaches two devices directly. The arbitrated loop topology attaches devices in a loop. The fibre channel fabric topology attaches host systems directly to a fabric, which are then connected to multiple devices. The fibre channel fabric topology allows several media types to be interconnected.
Fibre channel is a closed system that relies on multiple ports to exchange information on attributes and characteristics to determine if the ports can operate together. If the ports can work together, they define the criteria under which they communicate.
In fibre channel, a path is established between two nodes where the path's primary task is to transport data from one point to another at high speed with low latency, performing only simple error detection in hardware.
FC-AL is one fibre channel standard (incorporated herein by reference in its entirety) that establishes the protocols for an arbitrated loop topology. Conventional elements in a FC-AL topology are not robust and do not provide an efficient way to identify, isolate and manage loop traffic.
One such problem is shown in system 210 of FIG. 2B. System 210 includes a fibre channel element (or a switch) 216 that couples host systems 213-215 to storage systems 217 and 218. Storage system 217 and 218 include redundant array of independent disks (RAID) 211 and 219 coupled via plural input/output (“I/O”) modules (212) and RAID controllers 201A and 201B. If drive 219 is defective, it may disrupt all traffic in common-access network 220. This can result in loop failure and lower performance of the overall network. To discover the defective device in a common-access network, the system administrator may have few options other than removing devices until the network disruption ceases.
Another example is shown in FIG. 2A, where a RAID controller 201 is coupled to two different loops 209A and 208A via links 209 and 208 in a disk array system 200. Each loop has a small computer systems interface (SCSI) enclosure services (“SES”) module 202 and 202A. SES modules 202 and 202A comply with the SES industry standard that is incorporated herein by reference in its entirety.
Port Bypass Circuit (or PBC) modules 203 (and 206) couple plural disks (for example, 204, 202B and 207) and link 205 couples the PBC modules.
If drive 202B, which is dual ported, fails then both loops 209A and 208A are disrupted. Again, conventional techniques will require that storage 202A be removed and a bypass command issued to all drives, which takes the entire array off-line. Each device is attached and detached to investigate the reason for a link failure. Then all the drives, except the faulty drive are re-attached and loop activity is restored. This system of trial and error is labor intensive and inefficient.
Therefore, what is required is a process and system that can identify, isolate and manage loop faulty devices in common access networks, including the FC-AL topology.